For most clinical indications, the oral route of drug administration is not only the most convenient but is also associated with higher patient compliance. In the vast majority of cases, orally administered drug products must disintegrate and dissolve in the stomach before permeating the mucosal membranes of the stomach and intestines to reach the systemic circulation. Since key determinants of intestinal absorption (i.e. solubility, dissolution and permeability) are extremely difficult to obtain in vivo, especially in humans, in vitro tools to evaluate these parameters are necessary. Although there are in vitro techniques that independently permit the determination of permeability of the drug substance and the dissolution rate of the final drug product, there is currently no generally accepted scientific method for integrating both the dissolution rate and permeability data to predict the potential outcome in humans.